This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-261480, filed Aug. 30, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a lens-fitted film unit which can provide sharp photographs in various photographing environments.
2. Description of the Related Art
Lens-fitted film units each comprising a unit body fitted with built-in simple photographing means such as a taking lens, a shutter and a film winding up, wherein an unexposed photographic film has been charged at the time of manufacturing thereof, are being marketed. The lens-fitted film units, because of, for example, the readiness thereof, are contributing to the familiarization of photographs. Some types of lens-fitted film units are fitted with built-in strobes which enable photographing during the night, indoors, etc., and are being used by a large number of users.
These lens-fitted film units are provided with various measures for improving the performance thereof. In particular, attention has been drawn to the problem of unsuccessful photographs caused by under-exposure at indoor photographing because of such restrictions that it is needed to cope with a variety of conditions such as photographing in bright outdoor scenes and indoor strobe photographing, despite the absence of any exposure controlling function or only with a simple exposure controlling function, and that only a strobe of small guide number can be provided because of, for example, cost and compactness. Jpn. Pat. Appln. KOKAI Publication No. (hereinafter referred to as JP-A-5-188454 discloses under-exposure preventive measures comprising employing an EV value of 11 to 13.5 with respect to a film unit and employing a guide number of 10 to 15 with respect to a strobe. JP-A-6-258787 discloses a method of providing satisfactory photographs through every photographing including indoor photographing and outdoor photographing with the use of a lens-fitted film unit fitted with a built-in lightsensitive material having a scope of specific photographic speeder in a region of 640 or more and point gamma of 0.4 or more. Further, JP-A-8-184944 discloses under-exposure preventive measures for strobe photographing by the use of a lens-fitted film unit fitted with shutter speed switching means interlocked with strobe switching means. Also, JP-A""s-9-5817 and 10-260507 disclose under-exposure preventive measures by switching an aperture in accordance with the luminance of a subject.
Furthermore, JP-A-2000-131727 describing a prior invention of the present applicant discloses a method of optimizing a density, especially a density ratio between background and main subject exposed to strobe flashing, by the use of a lens-fitted film unit which satisfies the conditional formula:
xe2x88x926xe2x89xa62 log2(A)+log2(1/T)xe2x88x92log2(0.3xc3x97S)xe2x89xa65
wherein T represents the shutter speed of shutter (sec), A represents the stop value of aperture and S represents the ISO speed of photographic film.
These inventions exert respective effects, and have exerted marked effects especially in the improvement of under-exposure dull photographs.
It is an object of the present invention to provide a lens-fitted film unit which enables providing photographs being excellent in sharpness, i.e., another important performance of photographs.
More particularly, the object of the present invention is to provide a lens-fitted film unit which reconciles providing photographs being excellent in sharpness and implementing under-exposure preventive measures for photographs as aforementioned.
The above objects could be attained by the following means.
(1) A lens-fitted film unit comprising photographic mechanisms including a taking lens, a shutter device and an aperture, and having been loaded with an unexposed photographic film, wherein the shutter device and the photographic film satisfying the conditional formula:
log2(1/T)xe2x88x92log2(0.3xc3x97S) less than xe2x88x921.7
wherein T represents a shutter speed of the shutter device and S represents an ISO speed of the photographic film.
(2) The lens-fitted film unit as defined in item (1) above, wherein the unexposed photographic film comprises at least two blue-sensitive silver halide emulsion layers with different photographic speeds, at least two green-sensitive silver halide emulsion layers with different photographic speeds and at least two red-sensitive silver halide emulsion layers with different photographic speeds, on a support, wherein at least one of the blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers with the maximum photographic speeds contains a silver halide emulsion in which 60% or more of the total projected area of grains contained in the silver halide emulsion is occupied by tabular grains having an aspect ratio of 5.0 or more; and wherein, with respect to the silver halide emulsion contained in the at least one silver halide emulsion layer having the maximum photographic speed and containing the tabular grains, the grain number defined by the following formula (I) is 1.00 or less,
grain number=AH/(Dc2xc3x97Th)xe2x80x83xe2x80x83(I)
wherein
AH: a silver coating amount in terms of silver of the silver halide contained in the layer with the maximum photographic speed (g/m2),
Dc: an average equivalent circle diameter of the tabular grains contained in the layer with the maximum photographic speed (xcexcm), and
Th: an average thickness of the tabular grains contained in the layer with the maximum photographic speed (xcexcm),
provided that, when each of the at least one layer with the maximum photographic speed contains a plurality of silver halide emulsions which was prepared by separate production processes and which contains silver halide grains of different average equivalent sphere diameters, it is only required that the above limitations with respect to the aspect ratio and grain number be satisfied with respect to the emulsion having the maximum average equivalent sphere diameter.
(3) The lens-fitted film unit as defined in item (1) above, wherein the unexposed photographic film comprises at least two blue-sensitive silver halide emulsion layers with different photographic speeds, at least two green-sensitive silver halide emulsion layers with different photographic speeds and at least two red-sensitive silver halide emulsion layers with different photographic speeds, on a support, wherein the blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers with the maximum photographic speeds each have a silver content of 0.3 to 1.3 g/m2; and wherein at least two of the blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers with the maximum photographic speeds each contain silver halide grains in which 60% or more of the total projected area of the silver halide grains is occupied by tabular grains having an aspect ratio of 5.0 or more.
(4) The lens-fitted film unit as defined in item (1) above, wherein the unexposed photographic film comprises at least two blue-sensitive silver halide emulsion layers with different photographic speeds, at least two green-sensitive silver halide emulsion layers with different photographic speeds and at least two red-sensitive silver halide emulsion layers with different photographic speeds, on a support, wherein the blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers with the maximum photographic speeds have the total silver content of 1.5 to 3.5 g/m2; and wherein at least two of the blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers with the maximum photographic speeds each contain silver halide grains in which 60% or more of the total projected area of the silver halide grains is occupied by tabular grains having an aspect ratio of 5.0 or more.
(5) The lens-fitted film unit as defined in any of items (2) to (4) above, wherein the tabular silver halide grains are those:
(a) whose average silver iodide content is in the range of 2 to 10 mol %,
(b) whose surface silver iodide content is in the range of 1 to 4 mol %, and
(c) having 10 or more dislocation lines per grain.
(6) The lens-fitted film unit as defined in any of items (1) to (5) above, which further comprises photometric means capable of outputting a light quantity signal corresponding to a subject light quantity, and a controlling mechanism capable of changing an exposure quantity to the photographic film in accordance with the light quantity signal.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.